Many different shapes of packs and many different materials are known for making packs for packing liquids. Manufacturers are constantly seeking to make better packs more cheaply and preferably also so that they are environmentally-friendly. The packs are intended to be closed sealingly with a pouring device. While nonetheless presenting no significant problems to the end user when the packs are opened and the contents poured out. The very many kinds of packs include those which have a hole in the top which is closed by means of a pouring device which can be opened. While packs which are made of plastic-coated paper are known for keeping and transporting liquids, the present invention is concerned, in particular, with liquid packs made of plastic material wherein the hole in the top of the pack is surrounded by a collar which is like a partially cylindrical casing in shape and which has a central axis which is to be imagined as being disposed approximately vertically, but which can also be disposed at a certain angle to the perpendicular in special kinds of packs. The axis is taken as being a vertical central axis in the description of the present invention. The invention also relates to a pouring device, at least one part of which has a cup-shaped recess with a flange, with, on the outside, at least one wall which is like a partially cylindrical casing comparable to the afore-mentioned collar and of comparable diameter, so that the flange of the pouring device can be inserted into the collar of the hole. Liquids containers with lids which are closed in this way are known in the form of tin cans. However, the lid there is only capable of being opened if it is removed from the collar of the hole or from the tubular can, since cans of this kind do not have any special kind of top. However, seal-tight closure and also a good opening capacity are more problematic with pouring devices for liquids packs which have a top where only part of the upper surface is in the form of a hole. Pushing the flange of the pouring device into the collar of the hole is clearly only adequate for the purpose of sealing it from dust, but in order to close a pack for liquids so that it is seal-tight it is not enough by itself, not even if radial deformations are made to the flange and collar to provide undercut regions, snap-closure means, retaining means, or the like.
Those skilled in the art know that closure means have to be provided for liquids packs which are liquid-tight and even gas-tight.
Plastic containers are, admittedly, already known for packing, storing and transporting liquids. However, the manufacturing process and closure operation have hitherto always been somewhat tedious, and the present invention aims to overcome this. In the case of packs or pouring devices coated with plastic material, or with packs made of plastic material alone without any backing material, it is conceivable to join the pouring device to the pack using welding or sealing methods. However, this generally gives rise to problems. For example, in order to seal one plastic material to another, that is to say to sealingly join the flange of the pouring device to the collar of the hole in the pack, a temperature of 180.degree. C. is required in order to obtain a pack which is reliable and usable. Sealing premanufactured pouring devices to the holes of separate packs is a difficult undertaking when such a temperature is required, and for this reason pack manufacturers have already gone over to forming the pouring devices integrally with the top of the pack, or to manufacturing them by injection moulding techniques. Another problem when sealing jaws are used to join the afore-mentioned parts is the fact that the sealing surfaces have to be heated from the outside through the layers of material, wherein care must at the same time be taken to ensure that the press-on operation is good and correct in shape. Those methods have not brought the desired success because a number of problems have made the manufacturer recognize that the material strength of the plastics parts to be joined is often not exactly the same, and even if they only differ slightly in respect of material strength, gaps occur which cannot be closed by sealing.
Packs are conceivable which are composed of two parts, such that after the pack has been manufactured the joined seam extends transversely through the top and even through the hole in the top, so that a mismatch occurs in the region of the seam during the welding operation. That results in gaps which would have to be sufficiently filled with weld material and closed when the flange of the pouring device is inserted. Insurmountable problems arose here, particularly when a plurality of packs was to be closed simultaneously, in mass production, using the afore-mentioned pouring devices. One single pouring device has to be arranged on one single hole with great precision, and this cannot be done without effort. This method of closing packs is obviously more problematical with mass production, when, for example, five, ten or more packs are to be closed simultaneously, since it would appear that it is very difficult to place the pouring device in the holes accurately and then at the same time to seal it in place.